Container closure and seal



CONTAINER CLOSURE AND SEAL Filed Sept. 14. 1966 INVENTORS RICHARD W.ASMUS ANDREW E. JECKER BY ATTORNEYS United States Patent 8 ClaimsABSTRACT OF THE DISCLOSURE A container closure has a seal made of anoverplasticized plastisol. When the closure is tightened the plasticizerbleeds from the plastisol and wets the interface =between the closureand container.

This invention relates to closures for containers, and, moreparticularly, to very readily removable and resealable closures forcontainers, particularly rigid containers and packages.

With minor exceptions, such as glass containers employing tapered groundglass-to-glass seals, most closures for rigid containers, andparticularly, resealable closures depend upon deformation of a sealingmember engaged between the container at its opening and the closuremember. Examples of such deformable sealing members are the familiarrubber jar rings, the cork lining and spots of crown closures, the gummysealants or lutings lining the crimped joints of tin cans, and the like.

The closures made according to this invention overcome a long existentneed of container closures, namely, a container closure that effectivelyand efiiciently closes and seals after the contents are packaged thereinbut which may be readily opened and re-closed. A particular advantage ofthis invention is that it may be applied to conventional reclosablecontainer closures without requiring significant, if any, changes in theequipment for manufacturing them or for alteration or modification ofthe package closing equipment employed in conventional packagingmachinery. The absence of this feature has been an economic obstacle tomany eflForts heretofore made to improve and simplify the opening andclosing of container closures. Another advantage of this invention isthat the very physical characteristic of the sealing element of closuresmade according to this invention which effects its scaling function alsoallows it to function as a lubricant which makes the container easilyopened and rescaled.

Other objects and advantages of this invention will be apparent from thefollowing specification, claims, and drawings, in which:

FIGURE 1 is a fragmentary elevation, partly in section, of one specificembodiment of this invention, namely, a screw threaded closure capsecured on the mouth of a necked glass bottle.

FIGURE 2 is a fragmentary elevation, partly in section, of awide-mouthed metal can closed by a metal lid. The relative thicknessesand proportions of the several components are distorted for purposes ofillustration of these two exemplifications of the many types ofcontainers and closures in which this invention may be employed.

As shown in FIG. 1 of the drawings, the bottle 10 is provided with aconventional closure thread 11 molded therein below the rim 12 of thebottle mouth. The bottle is closed by a conventional metal cap having aclosure thread 21 formed in the depending skirt thereof, and an annularwell 22, in which the rim 12 may be received, the Well and rim beingspaced by the sealant 30. The inside of the cap may carry the usualliner or spot 23 of inert metal, film, or paper carying an organiccoating or laminated film to protect the metal of the cap from corrosionby the packaged contents and the contents from contamination orappearance of contamination by such corrosion.

In the bottle closure illustrated in FIG. 1, the sealant 30 may beconfined in the conventional manner to the well 22 so that it may bedeformed and provide sealing contact with the surface of the rim 12only. In this preferred embodiment of a screw-top closure, however, thesealant 30 extends down the inside of the skirt of the cap 20,particularly so as to line the load-carrying inner surface of the thread21 in order to take full advantage of the lubricating property of thematerial of the sealant 30.

In FIG. 2 a can has interrupted threads 111 formed adjacent the bead 112rolled at the mouth of the can. The can is closed by a conventional caphaving inwardly extending lugs 121 formed in the depending skirt of thelid. An annular well 122 is formed in the cap 120 and is filled with asealant 130. It is to be noted that in this embodiment in which only thewell 122 is filled with the sealant, rather than having the sealantextend down inside the cap and between the lugs 121 which engage theunderside of the thread 111, the width of the well is preferablyslightly greater than the width of the bead 112 and the bead does nottouch either side of the well. The depth of the well is preferably equalto or greater than the width of the bead. This construction permits, dueto the elastic property of the sealant 130, a tight seal for contentspackaged under pressure or vacuum, while allowing the cap to be openedor reclosed with a minimum of torque applied to disengage or engage thelugs 121 from the threads 111.

The sealant 30 or is an over-plasticized plastisol or organisol of anelastomeric thermoplastic resin, usually a vinyl homopolymer orcopolymer or a mixed homopolymer and copolymer, such as a mixture ofvinyl chloride and vinyl chloride-acetate. The term over-plasticized asused in this specification and its appended claims means that theplasticizer, as a non-volatile, relatively inert solvent or partialsolvent for the resin is incompletely dissolved in the resin and bleedsas a slippery liquid film on the surface of the resinious sealant at theexpected temperature of use of the closed container. Thus, theplasticizer may be a single solvent for the resinous component but inexcess of the proportion which the resin can ell ectively and compatiblydissolve or absorb at room and storage temperatures for the productspackaged in the closed container. Or the plasticizer may be a mixture ofsolvents comprising one liquid which is fully dissolved or absorbed inthe resinous compound and a second less compatible liquid which is asolvent or swelling agent for the resinous component at the gelling and/or fusing temperatures of the plastisol or organisol but which is atleast partially thrown out of solution when the gelled or fusedplastisol returns to storage temperatures. Or the plasticizer maycomprise a nonvolatile liquid which is fully incompatible with the resinat any temperature less than that at which the resin chars ordissociates but which couples directly or through a coupling agent withthe non-volatile solvent for the resin.

The over p'lasticized sealant, as applied in the closure at and duringthe time of use may be either gelled or have been subjected tosufficiently higher temperatures beyond that at which gellation hasoccurred to bring the plastisol to a state of fusion or at least partialfusion. Plastisols which have been merely gelled may be perfectlysatisfactory as sealants for closures or as lutings for container jointswhich may never be opened or opened only once. Due to the low tensilestrength and cheesy nature of plastisols which have been gelled but notfused, plastisols which have been brought to their fusion temperaturesto develop full strength and toughness are generally preferred as thesealants for closures which may be repeatedly opened and closed.

The use of an over-plasticized fused or gelled resilient plastisol as asealant for a closure represents, in many respects, a backward step inthe plastisol art, since heretofore an objective of the developments inthe plastisol art has been to avoid the bleed or often greasy feel ofthe early plastisols. It is acknowledged that, in the light of thecomplex physical chemistry of plastisols and organisols, the followingexplanation of the operation and function of an over-plasticizedplastisol as the sealant in closures made according to this inventionmay be, if not wholly incorrect, at least over-simplified.

Being a resilient composition, an over-plasticized plastisol, whenemployed as the material of a sealing member, of which the sealingmembers 30 and 130 are exemplifications, deforms under pressure toaccommodate surface deviations in the area of contact between a sealingmember and a container and its closure member. At the same time, such anover-plasticized plastisol is believed to behave as though it were asponge having molecularsized interstices in which the non-volatileplasticizing liquid is carried. Thus, the local pressure in the area ofsealing contact on a sealing member made according to this inventionneed be only sufiicient to deform the sealing member until itaccommodates the deviations from the geometrically true surface of thesealing areas sufficiently to permit the plasticizing liquid to wet and,thereby, seal the interface between the sealing member and the adjacentcontainer or closure. Accordingly, whereas a conventional resilientsealing member would require that the sealing member, to be effective,must be very tightly clamped between a container rim and closure tocreate very high localized ceiling pressures, a sealing member madeaccording to this invention need have only a comparatively loose fit.

The foregoing is believed to explain why, when the sealing member isitself engaged between the two positions or elements of a container andclosure, as is the case of the sealant 30 carried in the threads 21 ofthe bottle cap 20, as shown in FIG. 1, minimal torque is required totwist the cap 20 off and on the bottle to break the seal and seal itagain. The liquid plasticizer carried by the over-plasticized plastisolof the sealing member 30 not only eifects a tight seal but alsofunctions as a non-drying lubricant to reduce any friction or dragbetween the threads of the bottle and cap. When there is no sealingmember between the elements of the container and the closure which clampthe sealing member, as in the case of the embodiment shown in FIG. 2,the lugs 121 need not be tightened on the threads 111 to a degreewhereby substantial resistance to opening and effectively reclosing thecontainer is required. The sealing member 130 need only be compressed tothe point that the plasticizing liquid carried by it wets the bead 112of the can 110. If a pressure differential exists between the contentsof the can and the ambient atmosphere, it is believed that sealing isaided by the very pressure differential; this may be due to the factthat the sealant need not be fully compressed and, thereby, becomesrelatively immobilized. Thus, if the contents are packaged under avacuum, air pressure exerted on the sealant between the outside of thebead 112 and the skirt of the cap will tend to wedge the volume of theresilient sealant 130 between the inside of the bead 112 and the well122. Likewise, if the pressure on the contents is greater thanatmospheric, then the sealant 130 will tend to be wedged between theoutside of the bead and the cap, effecting in either case a sealingpressure which is not carried entirely by the load "between the lugs 121and the threads 111.

Formulation of the plastisols from which the sealing members madeaccording to this invention are made may vary widely according to theparticular resins and plasticizers. The resins and plasticizers aredictated in many instances by the nature of the contents being packaged;that is, both the resin and plasticizers should be relatively inert withrespect to the packaged contents. A typical formulation of a suitablevinyl plastisol for many types of packaged contents is as follows.

Resins: Parts by weight High molecular weight vinyl chloride homopolymer45 Vinyl chloride acetate copolymer (96% vinyl chloride) 1OPlasticizers:

Dioctyl phthalate 30 Triethylene glycol l0 Adjuncts:

Stabilizer (cadmium naphthanate) 2 Pigment (titanium dioxide) 3 Theresins, in the form of fine powders, and the adjuncts are dry-mixed andthen stirred into the plasticizers, final stirring being under vacuum toprovide a creamy de-aerated liquid, which gels at the temperature of225- 250 F. and fuses at approximately 375 F. Sealing members such asthe members 30 or 130 may be cast directly in the caps 20 or or cast orinjection molded separately and then adhered in the closures by suitableadhesive, such as a phenolic varnish, depending upon whether the capsare painted or printed after or before receiving the sealing member.Whereas a resin-to-plasticizer ratio of 75:25 of the above resins andplasticizers will provide a dfully plasticized, if rather stiff and dry,elastomeric product, the above ratio of 55:40 provides anover-plasticized and relatively soft elastomeric product having asomewhat wet, i.e., greasy or slimy, feel.

It is to be understood that the term plastisol as used in the foregoingspecification and the appended claims does not exclude organisols inwhich a solvent for the resin includes a component which volatilizesduring gelling and/ or fusion, providing there is a residualnon-volatile solvent which leaves the resin over-plasticized. Nor is theterm plastisol limited to gelled and fused dispersions of vinyl resin orthermoplastic resin only, but may include, for example, polystyrene orrubbers which have been over-plasticized or over-extended with aromaticoils.

What is claimed is:

1. In a rigid container having a seam therein, a sealing memberextending between and contacting adjacent surfaces of the seam, saidsealing member being a plastisol of an elastomeric resin containingsufficient incompletely dissolved non-volatile liquid plasticizer to wetthe interface between said member and a surface of the container seam.

2. A rigid container as defined in caim 1 in which said seam is the areaof contact between the mouth of a container and a closure therefor andthe plastisol of said sealing member has been at least partly fused.

3. A rigid container as defined in claim 2 in which said containerclosure is provided with an annular well and said sealing member islocated in said well and the mouth of the container is annular and maybe seated against said sealing member.

4. A readily opened and closed rigid container as defined in claim 3 inwhich the mouth of the container is held in engagement with said sealingmember by means providing a mechanical connection between the containerand the closure therefor.

5. A readily opened and closed container as defined in claim 4 in whichsaid connecting means comprises mating threads on said closure andcontainer and said sealing member extends between said threads.

6. A readily opened and closed container as defined in claim 4 in whichthe radial width of said annular well is greater than the width of theedge of the mouth of the container seated against said sealing memberand the depth of said well is at least the width of said edge.

7. The method of sealing a scam in a rigid container comprising thesteps of locating a sealing member consisting of an over-plasticizedplastisol between adjacent surfaces of the container at said seam andcreating sufficient pressure on said sealing member to bring it intocontact with and wet at least one of said surfaces with a non-volatileliquid plasticizer which bleeds from said plastisol.

8. The method as defined in claim 7 in which said seam constitutes anarea of contact between the mouth of a rigid container and a closuretherefor.

References Cited UNITED STATES PATENTS 2,726,001 12/1955 Cululi 215-40XR 2,874,863 2/1959 Unger et a1 215-40 3,215,297 11/1965 Acton et a1.21540 XR 3,231,529 1/1966 Kuhn et a1 215-40 XR 3,245,566 4/1966 Szalay215-40 DONALD F. NORTON, Primary Examiner.

US. Cl. X.R.

